(function (win,doc) {
	//浏览器缩放时
	win.onresize=function () {
	    change();
	};
	change();
	function change () {
	    var oFs=document.documentElement.clientWidth/(640/20);
	    //设置根目录字体大小
	    doc.documentElement.style.fontSize=oFs+'px';
	}
})(window,document);